Duplex radiotelephony



A. PRESS DUPLEX RADIOTELEPHONY Sept. 28 ,1926.

FiledJuly 30 1920 Illl INVENTOR Abra/Mm Pres) BY ATTORNEY I Wrmsssss:

Patented Sept. 28, 1926.

UNITED STATES PATENT OFFICE.

ABRAHAM PRESS, OF WILKINSBURG, BENNSYIJVANIA, ASSIGNOR '10 "WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

DUPLEX RADIOTELEPHONY.

Application filed July 30,

My invention relates to wireless telephoning and it has, for one of its principal objects, a system whereby the operator is able to transmit and receive messages simultaously.

A further object is to enable the operator to selectively transmit and receivefrom a designated station to the exclusion of any other station of the group.

Further objects will make themselves manifest from the description accompanying the drawings and will be incorporated in the appended claim.

Figure 1 is a diagrammatic view of an embodiment of my invention.

Fig. 2 is a similar View of an alternative form of my invention.

Fig. 3 is a detail view of the switching elements associated with the transmitting circuits. I In Fig. 1, I have indicated a stopping condenser 1 associated with a grid 2 of a triode 8 having a hot cathode 4: for impress ing'upon a transformer element-5 speech entering a transmitter 6 assoc1ated with the said triode. Thus, the stopping condenser 1 is connected, in the usual manner, by means of a transformer coil 7, to the hot cathode 4. On the other hand, the transmitter 6 is in circuit with the associated trans former coil 7 and a battery 8. Again, the transformer element 5 is connected. across the hot cathode 4 and the associated plate 9 through a battery or generator 10.

Current through the transformer element 5 will, therefore, be modulated in accordance with speech entering the transmitter 6. However, in order to permit the reception of signals, the present invention contemplates charging and discharging the stop ping condenser 1 at such a time rate as to permit inoperative intervals, whereby the effect of the transformer element 5 is neutralized or deadened' during such inoperative intervals, whereas, during the operative intervals, the element 5 is enabled to impress its modulating character upon the antenna to send forth signals in accordance with speech entering the transmitter.

To this end, therefore, I connect a trans former coil 11 excited, preferably, from an ultra-audio frequency generator 12 by means of its associated transformer coil 13. However, I do not wish it to be understood that my invention is limited to the precise 1920. I Serial No. 400,084.

number of cycles for which the generator 12 may be. designed. Thus, the number of cycles may be less than four thousand or many times greater than that number. The

exact number is a matter of convenience or suitability for the purposes required. By

means of the generator 12, therefore, the

stopping condenser 1 will function properly for the transmission of speech signals only during the operatlve periods in which such condenser is charged with theproper sign.

Coupled to the transformer element 5 is a second element 5 connected to grid 14 and av hot cathode 15 of a triode 16. The plate 17 of said triode is connected to one end of a coupling coil 18 whereas the other end of the coupling coil is connected to the hot cathode 15 through a suitable generator 19.

A variable condenser 20 may also be con nected in shunt with the coupling coil for generatorin order that the modulating current passing through the coupling coil. 18 may impress its character upon theantenna system 21 when excited by such high-fretem but is excited from a high-frequency" quency generator through its associated coupling coil 18".

The high-frequency generator, it will be found, also comprises, preferably, a further coupling coil 18 in series with the coupling Whereas the latter is coupled to coil 18". I the antenna by virtue of theassociated coil 18, the additional couplingcoil 18 is arranged to be uninfluenced by the antenna coupling coil 18. The reason for this will apear later. A further coupling coil 18 is shown connected to a grid 22 of a triode 23. It is also connected to an eliminating coupling coil 18 for association with the coupling coil 18 in order to wipe out any di-. rect effects of the. highfrequency-generator circuit upon the triode 28. Thus, the gridlilament circuit of the triode 23 comprises a stopping condenser 2d, the coupling coil 18", coupling coil 18", and the hot cathode 25. The plate circuit, however, comprises the plate 26, telephone receiver 27 and the plate battery 28. In order to provide fractional speaking and transmitting periods in sequence, the stopping condenser 24 is excited densers 1 and 24 relative to the generator 12 are so arranged that, for one-half of the cycle, the stopping condenser 1 will be suit ably charged and the stopping condenser 24 will be discharged, whereas,ctor the second half of the cycle of the generator 12, the stopping con-denser 24- will be suitably charged and the stopping, condenser 1 will be discharged. By means of the two stopping condensers 1 and 24,1 am, therefore, able to provide inoperative and operati-ve intervals in sequence for the transmit tingand receiving devices of the above wireless telephone system.

As an alternative to the above automatic method of providing inoperative and operative intervals, I accomplish substan tial'ly the same result by purely mechanical means. Thus, in. Fig. 2, instead of the generator 10 being continuously connected to lllifi'lil'lllSfOIDlGl coil'v5, I provide a switching means .31, indicated in. Fig. 3, in order to alternately provide inoperative and operative intervals for the generator 10 relative to the transformer element Such switching means 81 comprises sliding contact 32 connectedto one end of the generator 10,.which contact co-operates with a seg ment 33 which, in proper time relationship, connects the generator 10 with the transformer element 5 and hot cathode 4. By properly coupling the generator 10 to the switch 31,. as by means ot a shaft 35,. it is possible to allocate suitable time intervals in sequence to the sending and receiving.

vGenerator 19 is similarly provided witha switch element 31 in order to. introduce power properly into the plate circuit 15 18 17. The two generators 19' and 10- and their associated switches are suitably coupled, as indicated by the dotted line 86, in order to provide a simultaneity in the functioning'ot the two generators.

It will be seen. that the antenna 2.1 of Fig. 1. is connected toa single coupling coil 18, whereas. in Fig, 2,1 alternatively provide two branches 118 and 21.8 for the antenna system, The two coupling coils just referred. to are connected byv means of. contactors 37 and 38 with switch elements 39 and 39 which are properly co-ordinated with respect to the switches. 31 of the transmitter portion of my invention in. order that, through. the operative sending periods, the antenna-coupling coil 218 may be connected to. the antenna, whereas, during the inoperative sending periods the coupling coil 118 may be properly connected to the antenna system 21 for the reception of signals. The receiver system, coupled to the coupling coil 118, is substantially similar to that of the receiver circuit indicated in Fig. 1. liowevcr, as an alternative, the coupling coil 18 in Fig. 2 is connected directly across the grid 22 and cathode 25.

In the operation of my invention, it is seen that I provide, in the main, an inoperative period and an operative period, the one for speech transmission and the other tor speech reception. about such time periods, I have shown two alternative methods, though other equivalentmethods will also fall within the scope of my invention. Thus, in Fig, 1, the inoperative and operative periods are ob tained' by alternately charging and discharging the two stopping condensers 1 and 24 otthe transmitting and receiving circuits. In Fig. 2, however, instead of charging, and discharging the stopping condensers, I have provided a mechanical switching means whereby the modulating generators 10-19 are disconnected from the transmitting circuits at the same time that the antenna-coupling coils are switched on' and off in order to provide proper periods for the reception of signals.

Having disclosed the nature, of my invention, what, I claim is:

In a radio system, a generator of highfrequency oscillations, an antenna upon which said oscillations are impressed, receiving means associated with said antenna, means actuated from said high-frequency generator to approximately counteract the effect upon said receiving means of the hightrequency oscillations impressed upon the'a-ntenna by said highsfrequency generator, signal-controlled means for modulating the high-frequency oscillations in theantenna and means operating at ultra-audio frequency tor alternately rendering'the modulating means and the receiving means inoperative, whereby during one half-cycleof said ultra-audio frequency said receiving means is inoperative and during the next halt-cycle thereof said oscillations are unmodul'ated and will not then interfere with the reception of signals by said receiving means.

. In testimony whereof, I have hereunto subscribed my name this 28th day of July, 1920.

ABRAHAM PRESS.

In order to bring 

